The technology of older vehicles requires suitable oils

Each fan of classic cars knows from hearsay or his own experience that modern high-tech lubricants with their highly efficient additives are not suited for the application in older vehicles. If they are used in oldtimers and classic cars they often attack sealants and metal alloys which used to be applied. Furthermore, highly additivated engine oils with cleaning properties solve deposits inside the engine which can cause obstructions in the oil passages and serious engine damages. Therefore, lubricants for older vehicles should be chosen carefully. Old operating manuals list classifications of engine and transmission oils which are no longer used. However, lubricant manufacturers, as for instance the German ADDINOL Lube Oil GmbH, still offer the respective products.

The first DIN standard (6547) for engine oils of 1933 was valid for motorcycles, passenger cars, trucks, tractors, motor boats and motor ploughs even. Depending on the application one differentiated between greased and ungreased raffinates; different seasons required mono-grade engine oils of different viscosities.

Depending on their flowability oils were usually classified according to Engler degrees until 1950. Then the SAE classification, defined back in 1911, gained more and more acceptance in Europe as well. SAE grades do not say anything on the quality but describe the oil’s flowability depending on temperature. Oils for winter application were marked with the letter "W" such as SAE 10W or 20W. Oils of SAE grades 30, 40 or 50 were used during summer. This meant at least two oil changes per year.

The SAE defines the viscosity; the API standard describes characteristics such as lubricity, ageing resistance or shear stability. At the beginning engine oils were classified according to API types "Regular", "Premium" and "Heavy Duty". Soon this rough classification was replaced by the API classifications valid until today:

- API S for four-stroke gasoline engines
- API C for diesel engines
- API T for two-stroke gasoline engines 

A second letter is added to these classes: the farther this letter is from "A" in the alphabet, the higher the specification of the oil.

The right choice
The selection of the suitable lubricants for classic and vintage cars depends primarily on the following parameters:

- manufacturers specifications
- specifications, e.g. API
- model year
- operating conditions and specific features (e.g. oil filter).

Old operating manuals define the viscosity in Engler degrees at 50 °C; usually the information is quite diversified. These classifications can be "translated" into the SAE grades valid today.

Concerning the additivation there is the following rule of thumb: the older the vehicle, the fewer additives should be used in the engine oil. In vintage and classic cars mineral oil based lubricants without additives or mildly additivated products at most should be applied. Synthetic engine oils – they arose after 1980 – are not suited for these vehicles because of their "modern" additives.

Good guides for choosing are the technical data sheets of lubricant manufacturers. For older vehicles (before 1970) the specification API SA, SB, SC and SD for gasoline engines or API CA, CB, CC and CD for diesel engines are possible. Generally, the older the vehicle, the lower the API specification should be, i.e. the letter added to the classes S, C or T should be nearer to A.

With the engine oils M 30 SAE 30 and M 50 SAE 50 ADDINOL offers products without additives according to API SA/CA for gasoline and diesel engines. Their viscosity in Engler degrees lies between 5.20 and 8.20 (at 50 °C), and for M 50 between 10.50 and 26.00.

Two-stroke engine oils
There are two kinds of lubrication for two-stroke engines: mixed and separate or fresh-oil lubrication. Usually classic vehicles are not equipped with a separate lubricant tank and therefore mixed lubrication is more common for these vehicles (mixing ratio 1:25, 1:33). Two-stroke engine oils for older vehicles are classified according to API TA (at the moment API TC describes the highest class). Modern two-stroke engine oils based on mineral oil, such as the mildly additivated ADDINOL Super Mix MZ 405, can be applied in classic vehicles. Usually they possess a pre-mixing component to ensure a quick and thorough mixing with fuels. 

Transmission oils
The viscosity of transmission oils is also given in SAE grades but a different classification system is used here. The technical requirements on automotive gear lubricants are described in the categories GL 1, GL 3, GL 4 and GL 5. Generally, mono-grade transmission oils according to API GL 1 and GL 3 are applied in classic vehicles, as for instance the ADDINOL transmission oils 80W, 90 or 140 with mild additivation.

Special oils for classic vehicles
Passenger cars with contact ignition and lubrication felt require a special oil for the pairing cam/contact breaker. Addinol provides a lubricant protecting the contact breaker against dry running conditions and damages in the long run. For underbody protection an anti-corrosion oil of a relatively high viscosity is recommendable as for example ADDINOL Anti-corrosion oil KO 220 C. It is based on high-quality mineral oil raffinates and does not contain any solvents. It just needs to be applied to the metal surfaces and is compatible with paints as well as materials of plastics, elastomers and further.  Other metal parts can be treated with the solvent-containing anti-corrosion fluid ADDINOL KO 6-F Spray possessing water-displacing and excellent penetrating properties.

German article published in kfz-betrieb 47-48/2009 (view German article here)